Pharmacology projects are underway to expand the understanding of the mechanism of various antitumor agents. Based upon this work, it is hoped that new agents with improved efficacy can be developed, or that agents presently available can be applied more rationally in clinical settings. Clinical and laboratory work have centered around four classes of compounds: (1) Nitrosoureas--The phase I clinical trial of chlorozotocin has been completed, demonstrating that the drug indeed has mild delayed bone marrow toxicity. Phase II trials to define antitumor efficacy are being initiated. In conjunction with the phase II trial, a radioactive pharmacokinetic protocol will also be activated to study the pharmacokinetics of this compound. In the laboratory, the L-glucose analog of chlorozotocin, L-chlorozotocin, has been investigated and has been demonstrated to have comparable antitumor activity, indicating that active glucose transport does not play a role in the structure activity characteristics of this compound.